The overall goals of this longitudinal study are to examine the etiologic determinants of young adult drug use/abuse and the consequences of use on the individual's functioning. The original sample in 1975 consisted of 976 mothers whose children's average age was 5 (T1). Subsequently, children and their mothers were interviewed when the children's average age was 13 (T2), 15 (T3), and 21 (T4). At T5, only the youth (average age 26) was interviewed. A sixth data collection (T6) is proposed to accomplish the following: (1) to examine interrelations and interactions of personality, family, peer, and ecological factors (starting in early childhood) as they affect the course of drug use/abuse over time (i.e., onset, stability, and change); and (2) to study the consequences of long-term drug use of adult intra- and interpersonal functioning. As in the past, separate interviews with young adults will be conducted in their own homes by trained interviewers. Scales with adequate psychometric properties measuring the independence variables will be developed from the interview schedules. The primary analytic techniques will be causal analysis and/or hierarchial or logistic regression. The significance of this study lies in its longitudinal design with in-depth intra- and interpersonal data available at several crucial stages of development. These data allow us not only to examine the pathways to drug use/abuse from the very beginning but also to study the course of drug behavior over time, i.e., the factors related to the subject's becoming more (or less) involved in drug use/abuse over a span of years. Such knowledge will help pinpoint those adolescents/young adults at risk for increased drug involvement and will provide detailed and specific guidelines for prevention and treatment. Our longitudinal study of the consequences of drug use is unique in that the long-term effects of use can be evaluated to see if their impact is cumulative. Identification of childhood and adolescent factors that can mitigate or compensate for the impact of drug consequences on later functioning would provide additional aids for effective prevention and treatment efforts.